diff --git a/Project.toml b/Project.toml
index c5e63e67..93091014 100644
--- a/Project.toml
+++ b/Project.toml
@@ -1,7 +1,7 @@
 name = "DynamicExpressions"
 uuid = "a40a106e-89c9-4ca8-8020-a735e8728b6b"
 authors = ["MilesCranmer <miles.cranmer@gmail.com>"]
-version = "1.4.0"
+version = "1.4.1"
 
 [deps]
 ChainRulesCore = "d360d2e6-b24c-11e9-a2a3-2a2ae2dbcce4"
diff --git a/src/Interfaces.jl b/src/Interfaces.jl
index be0f6020..346db23d 100644
--- a/src/Interfaces.jl
+++ b/src/Interfaces.jl
@@ -123,7 +123,7 @@ function _check_set_constants!(ex::AbstractExpression)
     return first(get_scalar_constants(ex)) ≈ x2
 end
 function _check_string_tree(ex::AbstractExpression)
-    return string_tree(ex) isa String
+    return string_tree(ex) isa AbstractString
 end
 function _check_default_node(ex::AbstractExpression{T}) where {T}
     ET = typeof(ex)